Patent GB-1381040-A (GB)
Title: Heat sealing head
IPC: B29C65/18
Filed: 1972-11-03
Abstract: 1381040 Seaming non-metallic sheet material; making bags FMC CORP 3 Nov 1972 [12 Nov 1971] 50673/72 Headings B5K and B5D A heat sealing head comprises a heat sealing bar 70 having an elongate recess 78 formed therein for receiving a part of an electrical heating element 80, a support bar 88 having a corresponding elongate recess 126 formed therein for receiving the remainder of the element 80, a post 110 connecting the bar 88 to a support beam 34, and a spring clamp 92 clamping the bar 88 to the bar 70 for accommodating expansion of the bar 70 relative to the bar 88, the element 80 being a free fit in the recesses 78, 126 to permit radial expansion therein. In a machine for making bags from heat sealable film, a flattened tubular web W, either gusseted or ungusseted, passes from a roll R, Fig. 1, through a dancer roll assembly 12 for providing uniform tension, between grooved draw rolls 14, Fig. 3, co-operating with stripper or guide fingers 15, and through a sealer S to transversely seal and sever the web W. Each bag passes between a movable draw roll 16 and a fixed roll 18 and is fed by a belt conveyer 20 to a corrugating station 22 and is ejected into an enclosure formed by adjustable stop plates 24 on a stacking table 26. The sealer S comprises a reciprocable head 30 and a fixed anvil 32. The head 30 comprises a sealing bar 70 having an arcuate groove 78, Fig. 5, therein to receive a tubular electrically energized heating element 80 one end of which is free to allow for longitudinal expansion thereof. A number of bars 88 each having a groove complementary to the groove 78 are clamped to the bar 70 by spring clamps 92 each including shoulder bolts 94 extending through clamp plates 100 urged apart by compression springs 102. The element 80 is free to expand in the grooves in the bars 70, 88 without binding therein and lateral expansion of the bars 88 is permitted by the bolts 94 passing through notches 104 each longer than the bolt diameter. Each bar 88 is connected to a reciprocable I- beam 34 by a single central post 110. To prevent vibration, but to allow expansion of, the element 80 a spring biased clamp block 120 is located between adjacent ends of the bars 88 and is gripped by a clamp 122 identical to the clamps 92. Notches 124 permit thermal expansion of the block 120 and a groove 126 engages the element 80. A film-severing knife 50 is secured to a bar 52 carried by brackets 54 pivoted about a rod 56 by springs 58 on a bolt 59 to urge the knife into operating position. The brackets 54 allow the knife 50 to be moved away to reposition a polytetrafluoroethylene impregnated glass cloth curtain 60 wrapping around shafts 62, 64 and extending under the bar 70. The anvil 32 is similar to the head 30 and comprises bars 138 held against a sealing bar 72 by spring clamps 140. The bars 138 are adjustably connected to a fixed beam 130 by posts 142. Clamp blocks (144), Figs. 2 and 4 (both not shown), and spring clamps (146) are also provided. Heat shields 42, 44 have upper web supporting flanges 46 and internal cooling tubes 48. The upper face of the bar 72 is covered with polytetrafluoroethylene impregnated glass cloth.